The present invention relates to a temperature-compensated zener diode arrangement in the form of a semiconductor integrated circuit consisting of several transistor structures formed within a common body of semiconductor material and interconnected by layers of metallization. The base-emitter pn junctions of the transistor structures are so connected in series relative to the direction of the total current flowing in operation that part of them are operated in the reverse direction up to the breakdown voltage as zener diodes, while the remainder are operated in the forward direction as forward-biased diodes. The emitter of the first transistor structure acting as a zener diode or the base of a transistor structure acting as a forward-biased diode and the collector thereof are connected to a first external terminal, while the emitter of the last transistor structure acting as a forward-biased diode is connected to a second external terminal, as is known in principle from German Offenlegungsschrift (DT-OS) No. 1,589,707 and the corresponding German Auslegeschrift (DT-AS), from German Offenlegungsschrift No. 1,639,173 and the corresponding German Auslegeschrift, and from German Offenlegungsschrift No. 1,764,251.
These temperature-compensated zener diode arrangements have such a low temperature coefficient that they can be used in varactor-tuned radio and television receivers, where they generate the temperature-stable and fixed bias necessary to tune the varactor diodes. To are energized this, the known temperature-compensated zener diode arrays are operated like conventional zener diodes, i.e., a conventional shunt regulator is formed by means of a series-dropping resistor having one terminal connected to an unregulated dc voltage source.
With the development of all-electronic tuners with touch-contact operation, remote control capability, and generation of the voltage values associated with the individual receive channels by means of a pulse train of variable pulse duty factor, a new mode of operation of the known temperature-compensated zener diode arrangements has come into use. The zener diode arrangements are periodically short-circuited by means of a switch connected across them and controlled by the pulse train of variable pulse duty factor. If operated with a fixed pulse duty factor for a longer period of time, the zener diode arrangements will reach a thermally stable state, but if the pulse duty factor is suddenly changed when another station is selected, i.e., when switchover to a different tuning-voltage value is effected, the thermal equilibrium corresponding to the present condition will not be reached until after a longer period of time, because the switchover to a different pulse duty factor changes the thermal load placed on the zener diode arrangement.
The problem shown could be solved by improving the temperature response, i.e. reducing the temperature coefficient, of the known temperature-compensated zener diodes by one to two orders of magnitude. Such an improvement using semiconductor technology would be prohibitively expensive, however.